Direct numerical simulation on the pyrolysis of materials with volatile residue layer

The effect brought about by the burning of cables and its effect on building fires poses many problems and challenges for researchers. One of the main reasons is that the numerical simulation of the pyrolysis process is especially difficult because of the presence of non-linear moving boundary conditions in the partial differential equations. This paper presents the results of a detailed numerical simulation of the pyrolysis process of materials with a volatile residue layer using partial differential equations. The movable region formula in this case was transformed to the fixed region formula, and a pre-evaluation iteration method was used for tracing the pyrolysis front. Numerical simulation results were found to compare well with those of the precise solution and integral model. The effects of the volatile char on the pyrolysis rate, varying with time were then obtained.     

Persistence of Invariant Tori on Submanifolds in Hamiltonian Systems

Summary. Generalizing the degenerate KAM theorem under the Rüssmann nondegeneracy and the isoenergetic KAM theorem, we employ a quasilinear iterative scheme to study the persistence and frequency preservation of invariant tori on a smooth submanifold for a real analytic, nearly integrable Hamiltonian system. Under a nondegenerate condition of Rüssmann type on the submanifold, we shall show the following: (a) the majority of the unperturbed tori on the submanifold will persist; (b) the perturbed toral frequencies can be partially preserved according to the maximal degeneracy of the Hessian of the unperturbed system and be fully preserved if the Hessian is nondegenerate; (c) the Hamiltonian admits normal forms near the perturbed tori of arbitrarily prescribed high order. Under a subisoenergetic nondegenerate condition on an energy surface, we shall show that the majority of unperturbed tori give rise to invariant tori of the perturbed system of the same energy which preserve the ratio of certain components of the respective frequencies.     

Atropisomerism of the C-1-C'-1 axis of 2,2',8,8'-unsubstituted 1,1'-binaphthyl derivatives.

The Suzuki coupling of optically active (S)-binaphthyl bromide 10 with (S)-binaphthyl boronic acid 11 produced a diastereomeric mixture of tetrahydroxyquaternaphthyls 4. The coupling products 4as well as their derivatives 5-7 can be considered as members of the family of 1,1'-binaphthyl-3,3'-diols. The C-1-C'-1 axis of all these compounds was found to have an unusually high rotational barrier. Generally, the barrier is higher for derivatives having more bulky substituents at the 3 and 3' positions.     

A novel class of model constitutive laws in nonlinear elasticity: Construction via Loewner theory

Using a solitonic connection, we show that the class of infinitesimal Bäcklund transformations originally introduced by Loewner in 1952 in a gasodynamic context results in physically interesting nonlinear model constitutive laws. We obtain laws previously used to model a variety of hard and soft nonlinear elastic responses. A natural extension of the latter leads to a novel class of model constitutive laws where the stress and strain are given parametrically in terms of elliptic functions. Such models allow a change in the concavity of the stress-strain law. Such behavior can be observed in the compression of polycrystalline materials or in the unloading regimes of superelastic nickel-titanium.     

Mössbauer spectroscopy of ferromagnetic oxygen-rich dicalcium cuprate Ca2CuO3+δ

Hyperfine Interactions - Stoichiometric Ca2CuO3 qualifies as a low-dimensional antiferromagnet. Nonetheless, oxygenated sintered samples of high-purity Ca2CuO3+δ, δ? 0.17, exhibited...     

Bifurcations and chaos in a semiconductor laser with coherent or noisy optical injection

This paper investigates theoretically the dynamical sensitivity of semiconductor lasers to external optical signals. Bifurcation analysis of ordinary rate equations, describing noise-free lasers with pure coherent external signal, reveals that considerable modifications to the extend and type of externally induced bifurcations and chaos are possible by tailoring of the laser active-medium and resonator configurations. Extending the analysis to stochastic rate equations, which describe lasers with spontaneous emission noise and noisy external signal, reveals further dynamical effects owing to the introduced random fluctuations. In particular, phase-fluctuations (incoherence) in the external signal can have a dramatic impact on induced bifurcations and chaos. The observed strong sensitivity of laser instabilities to the intensity and coherence of external signal can provide a very sensitive means to detect ultra low levels of laser radiation.     

Spectroscopic and laser properties of Nd:Gd0.8La0.2VO4 crystal

The polarised absorption and fluorescence spectra of Nd:Gd_0.8La_0.2VO₄ crystal are measured and compared to those of Nd:GdVO₄. CW laser properties of diode-pumped Nd:Gd_0.8La_0.2VO₄ crystal operating at fundamental wavelengths of 1.06 and 1.34 μm, as well as when intracavity frequency-doubled to 532 and 670 nm, have been studied. The maximum output powers at 1.06 μm, 1.34 μm, 532 nm and 670 nm are 1.18 W, 671 mW, 206 mW and 42 mW respectively, at a diode-launched pump power of 2.9 W. The threshold pump powers are 80, 267, 7 and 15 mW respectively.     

Blind adaptive identification of FIR channel in chaotic communication systems

In this paper we study the problem of blind channel identification in chaotic communications. An adaptive algorithm is proposed, which exploits the boundness property of chaotic signals. Compared with the EKF-based approach, the proposed algorithm achieves a great complexity gain but at the expense of a slight accuracy degradation.However, our approach enjoys the important advantage that it does not require the a priori information such as nonlinearity of chaotic dynamics and the variances of measurement noise and the coefficient model noise. In addition,our approach is applicable to the ARMA system.     

Synchronized cyclic capillary electrophoresis using channels arranged in a triangle and low voltages

Synchronized cyclic capillary electrophoresis (SCCE) makes use of a closed loop separation channel by which the same sample can be separated during many cycles. This enables the repeated use of the same voltage for separations such that a high total voltage, and thus high efficiency, is obtained for the synchronized components. This can be accomplished by using any type of polygon geometry for the separation channel; and calculations of the available field and number of connections needed for polygons from 3 to 5 sides are presented. Triangular designs have the advantage of using the lowest number of wells. Such designs are described, with two additional features compared to that of earlier work: 1. voltage connections that are much shallower than the separation channel, to reduce losses and dispersion at the intersections; and 2. corners that are narrower than the separation channels to reduce dispersion in the turns. Experimental data is presented for the separation of a mixture of amino acids, and for a DNA separation in a polymeric sieving matrix. The DNA separation is most sensitive to the corner dispersion problem, which reduces the observed efficiency for that separation.     

An alternating direction Galerkin method for elliptic problems with gradient nonlinearity

Several problems in many applications involve the solution of partial differential equations with gradient dependent nonlinearity. The numerical solution of the resulting nonlinear system is rather expensive. We present an alternating direction Galerkin method that allows much faster solution of the nonlinear system. The alternating direction formulation help reduce the problem into a sequence of nonlinear systems that may be solved very efficiently. Theoretical study of the convergence of the method will also be presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)